Interactions of pesticides, drugs, and other chemicals, particularly industrial solvents or household chemicals are being studied. The induction of liver microsomal mixed function oxidase systems in the rat and other species is studied as a first indication of possible influence on drug metabolism. Effects of these agents on other enzyme systems such as acetylcholinesterase of brain and aliesterases of brain, liver and serum are studied. Direct evidence of interactions between the pesticides, drugs, etc. are assessed by way of toxicity measurements (LD sub 50 or sublethal effects).